Notes On Properties Of Birnaviruses

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2.9.Characters of IBDV:
2.9.1.Properties of Birnaviruses: Virions are non-enveloped, hexagonal in outline, approximately 60 nm in diameter, with a single shell having icosahedral symmetry. Genome consists of two molecules of linear double-stranded RNA, designated A and B, approximately 6 kb p in overall size. Four structural proteins, and one or more non-structural proteins {RNApolymerase (transcriptase)}. Survives at 60 OC for 60 minutes; stable at PH 3 to PH 9. Member viruses occur in chickens (infectious bursal disease virus), fish (infectious pancreatic necrosis virus); picobirnaviruses have been detected in feces of humans and several species of animals, sometimes in association with diarrhea. Birnaviruses replicate in the cytoplasm without greatly depressing cellular RNA or protein synthesis. The viral mRNA is transcribed by avirion-associated RNA-dependent RNA polymerase (transcriptase-VP1) (James Maclachlan and Dubovi., 2011).
2.9.2.Antigenic characters: Eight virus strains isolated from fowl has been studied, two from turkey and one from duck by neutralization test, all the viruses were related but not identical and could be grouped into two serotypes of IBDV represented by one strain from fowl and one from turkey. Serotype II consisted of an antigenically homogenous group of viruses from turkey and fowl (McFerran et al., 1980). Two serotypes of IBDV have been distinguished by using the virus neutralization test. An IBDV vaccine

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